Abstract

Colorectal cancer (CRC) is among the most common types of cancer in both men and women and is associated with high mortality, particularly at advanced stages. Markers for defining individual risk signatures in CRC patients are of great clinical value, as they may allow for targeted therapies to improve outcomes in CRC patients. Epigenetic alteration such as promoter hypermethylation of gene, as well as genetic abnormality such as gene mutation, occurs frequently during the pathogenesis of human cancers. Recent studies exhibit the increasing observations that both epigenetic and genetic changes combine to determine the phenotype of cancer. Thus, in the present study, we examined KRAS and PIK3CA mutations and the methylation status of BNIP3, SFRP1, and Dkk1, and analyzed the correlation between these molecular alterations and the clinicopathological features of CRC. We aimed to clarify whether a combination of genetic and epigenetic alterations can be used to classify CRC patients in relation to their clinicopathological features and outcomes. Tissue samples from 122 CRC patients who underwent surgical resection were examined. The methylation status of SFRP1 and Dkk1 and the sequences of exon 1 of KRAS gene and exons 9 and 20 of the PIK3CA gene were determined by methylation specific PCR and direct sequencing, respectively, using genomic DNA extracted from paraffin-embedded blocks. Correlation between these factors and clinicopathologic findings/patients survival were examined. As a result, there was a significant correlation between KRAS mutation and BNIP3 (p=0.0004) or Dkk1 (p=0.0009) methylation but not SFRP1 (p=0.114). Although SFRP1 and Dkk1 methylation showed no associations with disease specific survival (DSS) and other clinicopathological findings in CRC patients, BNIP3 was associated with poor DSS (p=0.0149). In CRC without both KRAS and PIK3CA mutation, patients with two or three methylated genes had poorer overall survival compared to those with no or one methylated genes (p=0.0017). To contrary, in the cases of at least one or more mutations, patients with two or three methylated genes tended to have better survival than patients with no methylation. Classifying CRC based on BNIP3, SFRP1, and Dkk1 methylation status and KRAS and PIK3CA mutation may be a clinically powerful predictor of patient outcome.